有限纠偏能力的多差速单元循迹协同控制

Cooperative Control on Multi-differential Unit's Tracking Performance with Limited Error-Correcting Ability

对于舱段、机翼等制造业常见的超大超重部件,使用重载AGV转运可提高其转运效率和安全性。由于双轮结构的差速轮具有更高的承载力和驱动力,重载AGV多使用差速轮驱动。但是,差速轮的特殊结构不仅使得轮系运动时内部左右两轮相互限制,同时配套在同一AGV上的多套轮系受车体刚性约束,轮系间及轮系内部的相互制约使得整车循迹灵活性不足。提出一种将基于偏差的控制律和基于驱动能力的控制律结合的多差速驱动轮系协同控制方法。该方法充分考虑差速轮运动学特性及整车刚体运动学特性;为保证AGV流畅运行,对各轮驱动速度进行限制,避免了电机频繁正反转和超出驱动能力的情况。此外,该方法易于更多轮系的扩展,轮系旋转中心不局限于车体中轴线,保证了实用性。仿真结果表明:该方法可根据位姿偏差决策、计算符合要求的驱动速度,有效协调位姿纠偏需求与轮系运动能力,使得误差被有效消除并最终达到稳定状态,实现差速驱动AGV循迹性能的整体优化。

For ultra-large and heavy components which are never uncommon in the aerospace industry such as bay section,wing,and so on,employment of heavy-duty automated guided vehicle(AGV)can help improve delivery efficiency and safety.Dif-ferential wheel that features higher bearing and driving capacities with dual-wheel structure is widely applied to AGV.However,the special structure causes two wheels to restrict each other when the system works,at the same time,and multiple differential wheels on the same ACV are restricted by the body rigidity.Restricting effect,either between systems or within the same wheel system,results in bad coupling and inadequate tracking flexibility for the overall vehicle.By combining error-based and driving capacity-based control laws,a multi-differential cooperative control system was proposed specific for system driven by differential wheels.In the method,taking the dynamic characteristics of differential wheel and the overall rigid body into full consideration,to guarantee the smooth opera-tion of AGV,all wheels were limited in terms of driving speed.Therefore,driving motors would not frequently switched between posi-tive and negative rotation and driving speeds would not exceed the driving capacity.In addition,the rotation center of each differential wheel was not limited to the center axis of car body which made the method easy to be extended to more units.The simulation results show that the method can make pose position-based decisions and figure out conforming driving speed.Its ability in effectively coordi-nating attitude correction demand with the wheel system's movement performance can significantly eliminate standing error and help the vehicle to achieve a final stable state.It proves efficient in accomplishing an overall optimization of differential-driven AGV's tracking performance.